Patch antennas for transreceiving radio-frequency signals are well known. Such patch antennas generally comprise a patch antenna element which is suitable for receiving and/or transmitting at a desired frequency range or bandwidth. These patch antennas may be linearly or circularly polarized, for example.
A conventional patch antenna is provided with a ground plate or ground plane which is parallel to the antenna and spaced apart therefrom. Thus, the ground plate has a patch side and a non-patch side. Patch antennas such as these are characterized their bore sight directionality (perpendicular to the plane of the patch antenna and in a direction pointed away from the patch side of the ground plate). The ground plate tends to shield or mitigate external signals emanating from non-bore sight directions. Similarly, the ground plate acts to control the direction of outgoing signals when the antenna is used to transmit signals.
Besides defining the directionality of the antenna, the characteristics of the ground plate impacts the antenna performance. It is understood that such a transmitting/receiving patch antenna results in electromagnetic fields emanating between the patch antenna and the ground plate and that the patch antenna and its ground plate have an inductive relationship. The nature of these electromagnetic fields impacts the antenna performance. As such, changing the size of the ground plate affects the antenna gain and pattern or shape. To a certain extent, the larger the ground plate, the greater the antenna gain and the more defined the antenna pattern. In a conventional configuration, the ground plate is larger than the patch antenna. Take for example a patch antenna which is rectangular and defines a length and a width. Typically, the associated ground plate requires a length and a width of approximately three times or greater than that of the patch antenna for optimum or increased antenna performance in terms of gain and pattern shape. Thus, the ground plate would have a surface area of at least nine times greater than the patch antenna.
Based on the foregoing, it is clear that the sizing requirements of such a patch antenna/ground plate arrangement is dominated by the size of the ground plate. In addition, it is understood that the sizing requirements of an antenna assembly directly impacts the overall weight of the assembly. The size and weight of an antenna assembly may impact the range of application of the device. Thus, under certain circumstances it is highly desirable to reduce the size and weight of the antenna assembly without sacrificing antenna performance. It is therefore evident that there exists a need in the art for a patch antenna assembly having a patch antenna with a relatively small ground plate thereby reducing the overall size and weight of antenna assembly.